1. Field of the Invention
The present invention relates to a solid electrolytic capacitor and a manufacturing method thereof.
2. Description of the Background Art
In accordance with recent trend in increasing the frequency of electronic equipment such as personal computers, instantaneous supply of current to electronic circuits is required. For this reason, it is desired to develop solid electrolytic capacitors having a smaller value of equivalent serial resistance (hereinafter referred to as ESR).
It is noted here that the ESR is the sum of dielectric loss, resistivity of an electrolyte, and contact resistance between the electrolyte and a cathode. In a high frequency region, the resistivity of an electrolyte and the contact resistance between the electrolyte and a cathode are predominant.
In general, cathodes formed by two layers, a carbon layer and a silver paste layer, are used for solid electrolytic capacitors (Electrochemical Society of JAPAN, ed., Electrochemistry Hand book (Denkikagaku Binran): MARUZEN CO., LTD), and in particular, in order to reduce non-uniformity of the connection strength between a cathode layer and a cathode lead terminal, the use of silver paste layers composed of silver particles having an average particle diameter of not smaller than 3 μm nor larger than 5 μm has been proposed (refer to JP-5-315200-A.)
In the above-mentioned solid electrolytic capacitor, however, the ESR in a high frequency region is affected by the contact resistance between the electrolyte and the cathode. In the case of a cathode formed by a carbon layer and a silver paste layer, in particular, the contact resistance between the carbon layer and the silver paste layer is attributed to a rise in the ESR, thereby making it difficult to reduce the ESR in a high frequency region.